Messages in this thread | | | From | Vincent Guittot <> | Date | Thu, 15 Sep 2016 16:51:55 +0200 | Subject | Re: [PATCH 4/7 v3] sched: propagate load during synchronous attach/detach |
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On 15 September 2016 at 16:43, Peter Zijlstra <peterz@infradead.org> wrote: > On Mon, Sep 12, 2016 at 09:47:49AM +0200, Vincent Guittot wrote: >> +static inline void >> +update_tg_cfs_load(struct cfs_rq *cfs_rq, struct sched_entity *se) >> +{ >> + struct cfs_rq *gcfs_rq = group_cfs_rq(se); >> + long delta, load = gcfs_rq->avg.load_avg; >> + >> + /* If the load of group cfs_rq is null, the load of the >> + * sched_entity will also be null so we can skip the formula >> + */ >> + if (load) { >> + long tg_load; >> + >> + /* Get tg's load and ensure tg_load > 0 */ >> + tg_load = atomic_long_read(&gcfs_rq->tg->load_avg) + 1; >> + >> + /* Ensure tg_load >= load and updated with current load*/ >> + tg_load -= gcfs_rq->tg_load_avg_contrib; >> + tg_load += load; >> + >> + /* scale gcfs_rq's load into tg's shares*/ >> + load *= scale_load_down(gcfs_rq->tg->shares); >> + load /= tg_load; >> + >> + /* >> + * we need to compute a correction term in the case that the >> + * task group is consuming <1 cpu so that we would contribute >> + * the same load as a task of equal weight. >> + */ >> + if (tg_load < scale_load_down(gcfs_rq->tg->shares)) { >> + load *= tg_load; >> + load /= scale_load_down(gcfs_rq->tg->shares); >> + } > > Note that you're reversing the exact scaling you just applied.
Yes, Indeed
> > That is: > shares tg_load > load * ------- * ------- == load > tg_load shares > >> + } > > So something like: > > shares = scale_load_down(gcfs_rq->tg->shares); > > if (tg_load >= shares) { > load *= shares; > load /= tg_load; > } > > should be the same as the above and saves a bunch of math, no?
Yes
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